1. Field of the Invention
The present invention relates to an ink-jet recording apparatus which jets an ink onto a recording medium.
2. Description of the Related Art
In ink-jet recording apparatuses described in Japanese Patent Application Laid-open No. 2009-196367 and Japanese Patent Application Laid-open No. 2006-167995 (FIG. 1), an intermittent transport operation of a recording medium in a transport direction and a reciprocative movement of a recording head in a scanning direction perpendicular to the transport direction are alternately repeated. An ink is jetted both in a forward scan of the ink-jet head and a backward scan of the ink-jet head to perform a recording operation (two-way printing, bidirectional printing).
In the two-way printing, in order to realize high printing quality, it is desired that a landing position (dot formation position) of the ink in the forward scan coincides with a landing position of the ink in the backward scan in the scanning direction. After the ink is jetted from each nozzle and before the jetted ink lands on the recording medium, the ink flies also in the scanning direction by the inertia caused by the movement of the recording head. Accordingly, it is possible that the landing position in the forward scan coincides with the landing position in the backward scan, provided that the actual ink jetting is performed based on a theoretical timing, which is obtained by scanning speed of the recording head and flying time of the ink (which is obtained by ink jetting speed and a gap between the recording head and the recording medium). In accordance with the theoretical timing, the ink is jetted before the dot formation position by a predetermined distance.
However, in fact, (1) every product is different in ink jetting speeds, (2) the ink jetting speed in the forward scan is not exactly same as the ink jetting speed in the backward scan, or (3) the gap between the recording head and the recording medium is not completely uniform. For the above (1) to (3) reasons etc., even if the ink is jetted at the theoretical timing (position) obtained as described above, a deviation is slightly caused between the landing position in the forward scan and the landing position in the backward scan. Therefore, it is necessary to adjust ink jetting timings in the forward scan and the backward scan from the theoretical timing.
In order to adjust the ink jetting timings in the forward scan and the backward scan, in the ink jet recording apparatus disclosed in Japanese Patent Application Laid-open No. 2009-196367, a pattern is formed on the recording medium by changing the ink jetting timing in the backward scan relative to the ink jetting timing in the forward scan in a stepwise manner. Then, the pattern which has the smallest deviation amount of the landing position is detected, and the ink jetting timings of the recording head in the forward scan and the backward scan are respectively adjusted to the ink jetting timings at which the pattern having the smallest deviation amount is formed. As such, the relative positional deviation of the landing position, in the scanning direction, between the forward scan and the backward scan is eliminated. Further, in the ink-jet recording apparatus described in Japanese Patent Application Laid-open No. 2006-167955, such a pattern is formed on each side of the recording medium in the scanning direction so as to perform landing correction relative to the gap at each of left and right ends of a platen.